Support dictionary as keyword argument and return

[amochin]

Dictionaries are called Property Lists in SenseTalk (eggplant language).

1. A dictionary passed as a keyword argument when calling an eggplant script in Robot Framework should be converted into a property list in format understantable for eggplant
2. A property list returned by an eggplant script should be converted into a dictionary understandable for Robot Framework

A dictionary may consist of Strings, Numbers, Lists and other Dictionaries:
{"key_one": "string_value", "key_two": 123, "key_three": ["list_item_1", 1234], "key_four": {"subdict_key_one": "subdict_str_val"}}